The current trend in increased numbers of MOEMS has resulted in multi-lens systems, where accurate alignment and mounting become important for the function of a composite device. Current methods of fabricating MOEMS attach individual lens elements to separate mounting structure(s), requiring alignment of at least two lens elements and a mounting system. Alignment errors can result in MOEMS having optical signal degradation and decreased function.
FIG. 1 illustrates a related art method of micro-lens alignment and placement (U.S. Pat. No. 5,963,577 to Synder et al.) The device displayed is directed toward a multi element laser diode incorporating a cylindrical micro-lens. In Snyder, the placement of the laser diode 110 and the micro-lens 121 is set by use of a spacer 108. The laser diode 110 and the spacer 108 are soldered onto the micro-lens 121. The alignment of the micro-lens 121 and laser diode 110 with the spacer 108 typifies the disadvantages of current systems. All are separate elements and thus must be aligned independently. In FIG. 1, the separate nature of the elements can result in alignment errors of the micro-lens with the spacer, alignment errors of the laser diode with the spacer, and alignment errors between the laser diode and the micro-lens.
FIG. 2 illustrates another related art system with multiple lenses and reflectors incorporated into a wavelength multiplexing transmitter and receiver module (U.S. Pat. No. 6,219,470 to Tu). A laser signal from a fiber optic cable 312 is wavelength separated by reflective surfaces 303 and 304, and wavelength dependent receivers 311 and 310 detect the separated wavelength signals. The reflective surfaces 303 and 304 are the result of multi-layer depositions on micro-machined grooves in the substrate material 301, which forms the base upon which the micro-lenses are attached. Tu again displays a disadvantage of current microlens mounting and alignment systems. The micro-lens 309A, 305B, and 309C are aligned separately, lending to the possible errors involved with individual alignment.
Alignment can be aided by using reference supports etched into the device showing where to place the optical elements. The etched supports can take the form of etched placement positions for placing previously formed micro-lens or can take the form of micro etched placement holes, micro pins, or other physical restraints and guide trenches. Although such holes, pins, and other physical constraints aid in alignment, alignment errors arise because the lenses must still be aligned individually.